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Which of the following observations is the BEST evidence that a sample of an unknown liquid is composed of only one pure substance?

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1 point
The sample partially freezes at one temperature.
The sample leaves behind a residue when filtered.
The sample boils away completely at a single temperature.
The sample appears cloudy with observable particles of different sizes throughout.
A student places several ice cubes in hot water. The ice cubes melt in the water, and the water becomes warm. The picture shows this process. Which of the following BEST describes the glass of warm water?
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1 point
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It is not a mixture because ice and water are two substances in two different states.
It is a mixture because ice and water are two different substances in two different states.
It is a mixture because the ice melted and combined with the liquid water in the same state.
It is not a mixture because the ice melted and combined with the liquid water in the same state.
A student makes two mixtures, both made of the same substances. What must be true of the two mixtures?
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1 point
Both mixtures have the same density.
Both mixtures have the same temperature.
Both mixtures are physically combined in the same proportions.
Both mixtures can be physically separated into its components.
What is one way to separate the different substances in a mixture?
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Option 1

Option 2

Option 3

Option 4
The picture below shows a chemistry experiment. Which statement best describes steps of this experiment?
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1 point
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Step one contains a compound, which is chemically combined in step two, forming a mixture in step three.
Step one contains a compound, which is physically combined in step two, forming a mixture in step three.
Step one contains one element, which is physically changed in step two, forming a new compound in step three.
Step one contains a mixture of elements, which are chemically combined in step two, forming a new compound in step three.

1 answer

Here are the answers to each of your questions based on the information provided:

  1. Which of the following observations is the BEST evidence that a sample of an unknown liquid is composed of only one pure substance?

    • Answer: The sample boils away completely at a single temperature.
    • Explanation: A pure substance has a specific boiling point, and if the substance boils completely at one temperature, it indicates that it is a pure substance.

  2. A student places several ice cubes in hot water. The ice cubes melt in the water, and the water becomes warm. Which of the following BEST describes the glass of warm water?

    • Answer: It is a mixture because ice and water are two different substances in two different states.
    • Explanation: The ice (solid state) and the water (liquid state) are indeed two different states of matter, thus forming a mixture.

  3. A student makes two mixtures, both made of the same substances. What must be true of the two mixtures?

    • Answer: Both mixtures can be physically separated into their components.
    • Explanation: By definition, mixtures can be separated into their individual components without a chemical reaction, regardless of their proportions.

  4. What is one way to separate the different substances in a mixture?

    • Answer: The correct option would depend on the provided images, which I cannot see. However, common methods for separating mixtures include filtration, distillation, or centrifugation.

  5. Which statement best describes steps of this experiment?

    • Answer: Step one contains a mixture of elements, which are chemically combined in step two, forming a new compound in step three.
    • Explanation: If step one is a mixture of elements and step two involves combining them chemically, then that forms a new compound in step three.

If you have images or specific options for the multiple-choice answers for questions 4 or 5, feel free to provide them for more tailored responses!